Tube supports

ABSTRACT

A vapor generator having a heat exchanger suspended within an upright gas passage wherein the heat exchanger comprises a first and second group of tubes and an arrangement for the support thereof including weldably connecting portions of said first and second group of tubes.

United States Patent 1 1 1 3,741,174

Rudd et al. June 26, 1973 TUBE SUPPORTS 3,267,913 8/1966 Bruhl 122 510 [75] Inventors: Alexander F 3,307,523 3/1967 Palchik et al... 122/510 x Hansen, both of Akron, Oh1o; 3310,04] 3/1967 James E. Ingersoll, Paris T Assignee: The Babcock & WllCOX Company,

New York, NY.

Filed: May 27, 1971 Appl. No.: 147,551

U.S. Cl. 122/510, 122/478 Int. Cl. F22!) 37/24 Field of Search 122/476, 478, 510

References Cited UNITED STATES' PATENTS 8/1966 Juchtern 122/510 Hansen et al. 122/5 10 Primary ExaminerKenneth W. Sprague Attorney-J. Maguire [57] ABSTRACT A vapor generator having a heat exchanger suspended within an upright gas passage wherein the heat exchanger comprises a first and second group of tubes and an arrangement for the support thereof including weldably connecting portions of said first and second group of tubes.

3 Claims, 7 Drawing Figures PAIENIEnJuuzs Ian A 3. 741. 174

' SHEET 1 or 2 FIG. 4 FIG. 3

o o 6 w 0 O O O O 7 O o O O O c o o o o x o 0 O D O O Y '0 0 o O O O 0 INVENTOR.

ALEXANDER H. RUDD WALTER A. HANSEN BY JAMES E. INGERSOLL PATENTEDJUH 2 6 I975 SHEET 2 [IF 2 FIG.

BACKGROUND OF THE INVENTION The invention relates generally to steam generators and more particularly to an arrangement for supporting horizontal tube banks suspended in a gaspassage of a steam generator.

The known arrangements include mechanical type supports which are in the form of elongated metal plates or rods, connected at the lower end to tubular heat exchange surface for the support thereof, and which extend upwardly through a gas passage and its associated roof portion for connection to the steam generator support structure. The use of mechanical type supports has been shown to have the following disadvantages; firstly, they are vulnerable to high gas temperatures which increase the rate of metal wastage and require frequent replacement and/or repair of the supports; secondly, the temperature of the metal plate or rod supports located in the gas stream will have a temperature approaching that of the surrounding gas stream while the supported heat exchanger tube members will be at or near the temperature of the fluid passing therethrough, resulting in an appreciable temperature difference between the supporting and the supported members with the latter being at a lower temperature. Thus,the metal supporting plates or rods will have a greater thermal expansion than the supported tubes and a rigid weld-tie between the supporting and supported members would give rise to excessive stresses and result in a possible rupture of the heat exchanger tube and/or failure of the weld-tie.

Another arrangement includes the use of fluid cooled support members, these may either be tubes from the supported heat exchanger circuit or tubes from a circuit other than the supported circuit. In either case, it is difficult to achieve an equivalence or low temperature difference between the supporting and supported tube members, particularly where the supported tubes are laid out in horizontal return-bend fashion thereby exposing substantially more heat exchange surface than the supporting tubes which normally extend in a gener' ally straight upright fashion. Thus, the temperature of the relatively short-run supporting tubes will be lower than that of the extended-length supported tubes. A disadvantage arising out of this arrangement is the resultant difference in thermal expansion between the supporting and supported members so that a weld-tie between the two members would give rise to excessive stresses leading to possible tube ruptures and/or weld tie separations. Where the supporting and supported tubes belong to the same heat exchanger circuit, there results an added disadvantage of having an appreciable difference in the temperature of the fluid exiting these respective tubes.

In both the mechanical and the fluid cooled type supports heretofore described, the present state of the art found it necessary to resort to a slidable or non-rigid tie between the supporting and supported members. These arrangements have proven uneconomical from the view point of initial capital outlay and from the frequent maintenance resulting in the replacement and/or repair of the mechanical type supports and the replacement and/or repair of the slidable tie connections in the mechanical as well as the fluid cooled type supports. Both the mechanical type supports and the slidable connections are vulnerable to a rapid rate of metal wastage since they cannot be adequately cooled.

SUMMARY OF THE INVENTION The present invention is concerned with providing an arrangement which includes adequately cooled support members and minimizes the metal temperature difference at the connecting ties between supporting and supported tubes and the temperature difference between the fluid exiting from the supporting tubes and supported tubes.

In accordance with the invention, there is provided a generally upright tubular heat exchanger formed of a plurality of banks suspended within a gas passage and including the means for passing a fluid to be heated therethrough. The heat exchanger includes a first and second group of interlaced tubes, each of the first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the first group of tubes to form one or more banks of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the returnbend sections of the next adjacent one of the second group of tubes to form one or more banks of second group of tubes. One or more fluid outlet headers being situated above the heat exchanger and one or more fluid inlet headers being situated below the heat exchanger. The tube portions connecting the inlet of the lowermost banks of the first and second group of tubes to the inlet header form the inlet legs and the tube portions connecting the outlet of the uppermost banks of the first and second group of tubes to the outlet header form the outlet legs. At least some of the inlet legs to the bank of second group of tubes extending vertically upward through the bank of first group of tubes in interlaced relationship therewith, these inlet legs extend along each alternate passage between vertical tube bank rows and are weldably connected to one or more portions of the pairs of return-bend sections in opposite-adjacent relationship thereto. At least some of the outlet legs of the bank of first vertically upward through the bank of second group of tubes in interlaced relationship therewith, these outlet legs extend along each alternate passage between vertical tube bank rows and are weldably connected to one or more portions of the pairs of return bend sections in opposite-adjacent relationship thereto. The inlet legs of the bank of second group of tubes which are weldablytied to the return-bend sections of the first group of tubes act as the supporting members for the bank of first group of tubes, these supporting inlet legs transfer the supported weight load to the outlet legs of the bank of first group of tubes which are also weldably-tied to return-bend sections of the second group of tubes, thus these supporting outlet legs'carry the weight load of the banks of both the first and second group of tubes. This weight load is 'in turn transferred through the one or more fluid outlet headers to the steam generator support structure. The load transfer point between the supporting inlet and outlet legs is located at the tube sections lying intermediate of the uppermost bank of first group of tubes and the lowermost bank of second group of tubesand is in the form of a welded-tie between adjacent inlet and outlet leg portions.

group of tubes extending FIG. 1 is a sectional elevation of a once-through forced flow steam generator embodying the invention. FIG. 2 is asectional side view of the heat exchanger and related support structure embodying the invention. FIG. 3 is a schematic plan view taken along line 3-3 of FIG. 2 and showing an interlacing arrangement between the supporting and supported tube members.

FIG. 4 is a schematic plan view taken along line 4-4 of FIG. 2 and showing an alternate interlacing arrangement between the supporting and supported tube members.

FIG. 5 is a detail end view of the load-transfer tie between the supporting tubes of the first and second group of tubes and ties between supported return-bend sections of the first group of tubes and the supporting tubes.

FIG. 6 is a detail side view of the load transfer tie between the supporting tubes of the first and second group of tubes. I

FIG. 7 is a detail plan view taken along line 7-7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the invention has been illustrated as embodied in a top-supported forced flow once-through steam generator intended for central station use.

The main portions of the unit, as depicted in FIG. 1, include an upright furnace chamber 10 of substantially rectangular horizontal cross-section defined by a front wall 12, rear wall 14, side walls 16, a roof 18, and a hopper and having a gas outlet 22 at its upper end opening to a horizontally extending gas passage 24 of rectangular vertical cross-section formed by a portion of nose arch 26 and extensions of the furnace roof 18 and side walls 16. Gas passage 24 communicates at its rear end. with the upper end of an upright gas passage 28 of rectangular horizontal cross-section formed by a front wall 30, a rear wall 32, side walls 34 and an extension of the roof of gas passage 24.

The fuel firing section comprises vertically spaced rows of burners 36 disposed on opposite walls 12 and 14 at the lower portion of the furnace chamber 10.

The gas passage 24 is occupied by a secondary superheater 38 and a reheater 40 arranged in series with respect to gas flow while gas passage 28 is occupied in the direction of gas flow by a primary superheater 42 and an economizer 44. It will be understood that in accordance with well-known practice, each of the secondary superheater, reheater, primary superheater and economizers extends across the full width of its corresponding gas passage and is formed for serial flow of fluid by multiple looped tubes.

The vapor generating setting is top supported by structural members including upright members 46 and cross beams 48, from which hangers 50, of which only a few are illustrated, support all walls and convection pass heat exchange surfaces.

The primary superheater 42, as shown, includes a lower bank 52 made up of a first group of tubes and an upper bank 54 made up of a second group of tubes. The primary superheater inlet header 56 supplies vapor to the inlet legs 58 of the first group of tubes for flow through the lower bank 52 and thence through the outlet legs 60 for discharge into the primary superheater outlet header 62. The inlet header 56 also supplies vapor to the inlet legs 64 of the second group of tubes for flow through the upper bank 54 and thence through the outlet legs 66 for discharge into the outlet header 62. The first and second group of tubes are interlaced with one another and the inlet legs 64 of the second group of tubes are connectively associated with portions of the return-bend sections of the lower bank 52 for the support thereof. The outlet legs 60 of the first group of tubes are connectively associated with portions of the return-bend sections of the upper bank 54 for the support thereof. The inlet legs 64 are connectively associated with corresponding outlet legs 60 at load transfer points 68 where the weight-load carried by the inlet legs 64 is transmitted to the outlet legs 60, these latter tube legs, in turn, transmit the sum of their weight-load and that of inlet legs 64 to the steam generator support structure by way of primary superheater outlet header 62 and corresponding hangers 50. It will be understood that there may be more than one bank of first as well as second group of tubes and that the number of banks between groups need not be identical. Also, that there may be more than one outlet and/or inlet header associated with the heat exchange surface formed by the first and second group of tubes.

In the normal operation of the steam generating unit, feedwater at high pressure is supplied by a feed pump, not shown, to the economizer inlet header 68, then passes through economizer 44 and its outlet header 70 and thence through appropriate headers and piping, not shown, for successive flow through the furnace boundary wall fluid heating circuitry, and through the wall fluid heating circuitry of the convection gas passes 24 and 28, and through to the primary superheater inlet header 56, being discharged therein in the form of vapor to be distributed between the first and second group of tubes for parallel flow through the primary superheater, both the first and second group of tubes include one or more banks of return-bend sections thus insuring that all these tubes are formed with adequate or substantially the same heating surface area thus resulting in a more uniform heated vapor temperature being discharged into the primary superheater outlet header 62, the latter being normally located out of the gas stream in a penthouse chamber 72 situated above the roof 18. The heated vapor leaving the outlet header 62 passes through attemperators, not shown, for further heating through the secondary superheater 38 and thence to the high pressure turbine, not shown, vapor leaving the high pressure turbine is returned to the steam generator for flow through the reheater 40 and then conveyed to the low pressure turbine, not shown. The combustion air and fuel are supplied to the burners 36 and the fuel is burned at the lower portion of the furnace. Heating gases flow upwardly through chamber 10 to the furnace outlet 22, thence to gas passage 24, and then pass successively over and between the tubes of secondary superheater 38 and reheater 40 in gas passage 24 and over and between the tubes of primary superheater 42 and economizer 44 in gas passage 28, and then discharge to an air heater, not shown, before entering the stack.

Referring to FIG. 2, there is shown a sectional side view of the heat exchanger and related support structure. The primary superheater inlet header 56 supplies fluid in a vapor state to the first group of tubes 74 and the second group of tubes 76 for parallel flow therethrough. Each of the first group of tubes 74 is formed of a generally upright inlet leg segment 58 followed by an intermediate segment 78 including a plurality of vertically spaced, horizontally extending return-bend sections 80, these return-bend sections comprising a lower bank 52 and followed by a generally upright outlet leg segment 60. Each of the second group of tubes 76 is formed of a generally upright inlet leg 64 followed by an intermediate segment 84 including a plurality of vertically spaced, horizontally extending return-bend sections 86, these return-bend sections comprising an upper bank 54 and followed by a generally upright outlet leg segment 66. Tube guide bars 88 are interspersed between banked rows of first and second group of tubes, respectively. The arrangement shown in FIG. 2 includes two pair of inlet leg segments 64 interlaced with every other row of first group of tubes and extending vertically across the bank 52, each pair being approximately a third of the way in from the respective ends of the bank. Each inlet leg 64 being weldably connected to portions of the first group of tubes oppositeadjacent thereto. The weld connections alternating so that each returnbend portion will be weldably connected to only one of the inlet legs. There are only two outlet leg segments 60 interlaced with every other row of second group of tubes and extending vertically across the bank 54, each leg being approximately a third of the way in from the respective ends of the bank. Each outlet leg 60 being weldably connected to portions of the second group of tubes oppositeadjacent thereto. To weld connections alternating so that each return-bend portion will be weldably connected to only one of the outlet legs. Each pair of inlet leg segments 64 is weldably-connected to an interlaced outlet leg segment 60 at the load transfer point 68.

Referring to FIG. 3, there is illustrated an interlacing arrangement between the.return-bend sections 86 of the second group of tubes and the outlet legs 60 of the first group of tubes. As shown, two outlet legs 60 extend vertically along each alternate passage between vertical tube rows with each tube being located inward from the corresponding ends of the return-bend sections. Each of the two outlet legs are laterally aligned with the next adjacent outlet legs to form two spaced rows of outlet legs 60, at least one outlet leg in each of the two rows being offset to provide an access-way to the space between rows.

Referring to FIG. 4, there is illustrated an interlacing arrangement between the return-bend sections 80 of the first group of tubes and the inlet legs 64 of the second group of tubes. As shown, two pair of inlet legs 64 extend vertically along each alternate passage between vertical tube rows with each pair being located inward from the corresponding ends of the return-bend sections. Each of the two pair of inlet legs 64 are laterally aligned with the next adjacent pair to form two spaced rows of pair of inlet legs 64, at least one pair in each of the two rows being offset to provide an access-way to the space between rows.

Referring to FIG. 5, there is illustrated a detail end view of the tube tie arrangement at the load transfer point 68 showing the return-bend sections 80 of the first group of tubes and the outlet legs 60 emerging therefrom and being bent into the same plane as the inlet legs 64 of the second group of tubes, the latter being, thereafter, bent-out to form the return-bend sections 86. A portion of the outlet legs 60 of the first group of tubes being weldably connected to a portion of an adjacent inlet leg 64 of the second group of tubes at the load transfer point 68 through a weldment clip 92. A portion of one of the return-bend sections being weldably connected to a portion of the adjacent inlet leg 64 through a weldment clip 90. A similar weldment clip connection is used between the return-bend sections 86 and the outlet legs 60.

Referring to FIG. 6, there is illustrated a detail side view of the tube tie arrangement at the load transfer point 68 showing the return-bend sections 80 of the first group of tubes, with the top section bending upwardly to form the outlet leg 60. A pair of inlet legs 64 of the second group of tubes being interlaced with the return-bend sections 80 and extending upwardly and each inlet leg having a portion weldably connected to a portion of an adjacent outlet leg 60 through a weldment clip 92 at the load transfer point 68. The pair of inlet legs 64, thereafter, bending to form the horizontally extending return-bend sections 86.

Referring to FIG. 7, there is illustrated a detail plan view of the tube tie arrangement at the load transfer point 68 showing a pair of inlet tube legs 64 of the second group of tubes lying in the same plane and in opposite adjacent relationship to the outlet tube leg 60 of the first group of tubes and weldably connected thereto through a weldment clip 92 interposed between the adjacent tube walls.

While in accordance with the provision of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

l. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combustion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the retum-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the bank of second group of tubes, each tube of said first and second group of tubes including end segments extending above and below respective banks to form respectively the outlet and inlet legs to said banks, and means supportingly connecting said first and second group of tubes wherein at least one inlet leg of said second group of tubes extends along each alternate passage between vertical tube rows of said first group of tubes, said inlet leg being weldably connected to at least one portion of at least one pair of return-bend sections in opposite adjacent relationship therewith.

7 2. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combustion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the endsthereof, the return-bend sections of each of the first group of tubes being laterally aligned with the retum-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the bank of second group of tubes, each tube of said first and second group of tubes including end segments extending above and below respective banks to form respectively the outlet and inlet legs to said banks, and means supportingly connecting said first and second group of tubes wherein at least one outlet leg of said first group of tubes extends along each alternate passage between vertical tube rows of said second group of tubes, said outlet leg being weldably connected to at least one portion of at least one pair of returnaband sections in opposite adjacent relationship therewith.

3. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combustion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the.

thereof weldably united to one another.

UNITED STATES PATENT OFFICE 7 I CERTIFICATE OF CORRECTION Patent No. 3,741,174 Dated June 26, 1973 Inventor(s) ALEXANDER H. RUDD, ET. AL.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column 6, line 62, cancel "at least one"; line 62, "leg should read legs line 63, "extends" should read extend v line 63, cancel "each"; lines 63 and 64, "passage" should read passages line 65, insert each of before "said";flline 65, insert last named before "'inlet"; line 65, "leg" should read legs Column 7, line 25, cancel "at least one"; line 25, "leg" should read legs line 26, "extends" should ,read extend line 26, cancel "each"; lines 26 and 27,- "passage" should read passages line 28, insert each of before "said"; line 28, insert last named before "outlet"; line 28, "leg" should read --legs Signed and sealed this 22nd day of January 1974.

(SEAL) Attest:

RENE D. TEGTMEYER EDWARD M.FLETCHER,JR.

Acting Commissioner of Patents Attest'ing Officer 

1. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combusTion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the bank of second group of tubes, each tube of said first and second group of tubes including end segments extending above and below respective banks to form respectively the outlet and inlet legs to said banks, and means supportingly connecting said first and second group of tubes wherein at least one inlet leg of said second group of tubes extends along each alternate passage between vertical tube rows of said first group of tubes, said inlet leg being weldably connected to at least one portion of at least one pair of returnbend sections in opposite adjacent relationship therewith.
 2. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combustion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the bank of second group of tubes, each tube of said first and second group of tubes including end segments extending above and below respective banks to form respectively the outlet and inlet legs to said banks, and means supportingly connecting said first and second group of tubes wherein at least one outlet leg of said first group of tubes extends along each alternate passage between vertical tube rows of said second group of tubes, said outlet leg being weldably connected to at least one portion of at least one pair of return-band sections in opposite adjacent relationship therewith.
 3. A vapor generating and superheating apparatus having an upright gas passage, means for conveying combustion gas through the passage, at least one generally upright tubular heat exchanger suspended within the passage and means for passing heated fluid through said heat exchanger wherein the heat exchanger includes a first and second group of interlaced tubes, each of said first and second group of tubes being formed with a plurality of vertically spaced return-bend sections intermediate the ends thereof, the return-bend sections of each of the first group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the first group of tubes to form at least one bank of first group of tubes, the return-bend sections of each of the second group of tubes being laterally aligned with the return-bend sections of the next adjacent one of the second group of tubes to form at least one bank of second group of tubes, said bank of first group of tubes being vertically spaced from the bank of second group of tubes, each tube of the first and second group of tubes including end segments extending above and below respective banks, and means supportingly connecting the first and second group of tubes wherein some of the segments of said first group of tubes include sections disposed contiguous to sections of some of the segments of said second group of tubes, said contiguous sections having at least a portion thereof weldably united to one another. 